The one-and two-electron spin-orbit integrals over the BP Hamiltonian can be precomputed and stored on disk using the command

`LSINT`[,`X`][,`Y`][,`Z`][,`ONECENTER`][;`TWOINT`,*twoint*;][;`PREFAC`,*prefac*;]

`X`, `Y`, and `Z` specify the components to be computed. If none of these
is given, all three are evaluated. The advantage of precomputing the integrals is that
they can then be used in any number of subsequent SO calculations, but this may require
a large amount of disk space (note that there are 6 times as many integrals as in an
energy calculation). If the `LSINT` card is not given, the integrals are computed
whenever needed.
The keyword `ONECENTER`
activates the one-center approximation for one- and two- electron spin-orbit integrals.
This can reduce drastically the computing time for large molecules. `TWOINT` and `PREFAC` can be used to
control the accuracy of spin-orbit integrals. These thresholds are similar to `TWOINT` and
`PREFAC` for standard integrals. The default value for `PREFAC` is `TWOINT/100`,
and the default value for `TWOINT` is . In the case when no integrals
are precomputed, these thresholds can be specified as options for `HLSMAT` or `TRANLS` cards, see below.

The input for spin-orbit ECPs is described in section 12. Of course, in ECP-LS calculations
the `LSINT` card is not needed.

molpro@molpro.net 2019-03-18